This commit updates information about how to contact the Fedora Council
and the best places to get in touch. This updates information about IRC
and mailing lists, and replaces them either with platform-agnostic
language or Matrix/Discourse specifically, where applicable.

This commit builds on what @mattdm already put together in January 2022
in PR #138. There is not a significant change to what was already voted
on and decided previously, but I did reorganize some of the content on
the "Contact" page in an attempt to enhance the page structure already
laid out. It includes @bcotton's feedback asked for previously.

These changes are a year old and do not include changes to the charter
other than links to the Council meetings wiki page and changing the
Discourse link from the old category to the Council tag. I intend to
merge this on commit, on the conditional affirmation by the Council has
approved this change during our February 2023 face-to-face meeting in
Frankfurt, Germany.

ref: Fedora-Council/council-docs#138